1. Field of the Invention
The present invention relates to electronic enclosure sealing devices and, more particularly, to a device and method of forming a unitary electrically shielded panel.
2. Description of the Related Art
Electromagnetic interference (“EMI”) is often the bane of electronic equipment and circuit designers. Federal regulations mandate that electronic equipment enclosures must not radiate electromagnetic signals that interfere with other proximately located electronic equipment. Electronic equipment enclosures must also be sufficiently shielded against interference from electromagnetic signals radiated from other proximately located equipment. The challenge to designers to control EMI becomes increasingly more difficult as the operating speed of electronic devices increases.
Currently, apertures defined in electronic equipment enclosures are sealed using electrically shielded panels, e.g. circuit-pack faceplates, blank filler panels, covers, doors, etc., that may comprise a separate panel part and gasket. A metallic panel part will function as a conductive shield that spans the enclosure opening to reduce EMI passage therethrough. Here, the gasket need only provide a perimeter seal between the panel part and the enclosure. The panel part may also be non-metallic, in which case a conductive paint or other similar conductive material must be applied to the surface of the panel part that is to receive the gasket. The conductive paint serves as a shield spanning the enclosure opening and the gasket provides a perimeter seal below the panel part and the enclosure. The gasket may be, for example, of metal, a metal-impregnated elastomer, or an elastomer wrapped in a metal sheath, and is affixed to the panel part in a subsequent operation after the panel part is formed. The gasket may be secured to the panel part by friction, adhesive, or by interlocking complementary parts on the panel part and gasket. In other words, fabricating an electrically shielded panel involves at least a two step process: 1) fabricating the panel part; and thereafter 2) affixing a gasket thereto.
U.S. Pat. No. 5,641,438 to Bunyan et al. discloses a method of extruding a fluent electrically conductive polymeric material onto a rigid substrate to form a polymeric EMI gasket thereon. The polymeric material is then cured to produce a bead-like gasket on the substrate. However, the gasket disclosed in this reference is extruded onto the substrate as a secondary operation only after the substrate is fabricated and provides only a perimeter electrical seal.
U.S. Pat. No. 5,524,908 to Reis discloses a multi-layered EMI gasket having first and second electrically conductive layers, with the second layer being more rigid than the first. The second layer must be conductive and generally malleable to permit bending, folding, notching and other forming of the disclosed EMI gasket. The layers may be secured together in a variety of ways including bonding, welding, laminating, or other art recognized affixation methods and techniques—ostensibly as a third step after the layers have been fabricated. However, after the EMI gasket disclosed in this reference is formed, it must then be fastened to or between a substrate or other rigid material before it may be used to electronically seal an enclosure opening.